BTW, this is our initial design. Will plan to make the top floor out of straw bale, we are researching the feasibility of mixed construction methods.

Husband is a heating engineer so he is playing with different heating systems if we find temp is not quite what we hoped, and we are planning to introduce a rocket stove mass heater that will incorporate underfloor heating and a hot water tank in that small understair cupboard to charge the thermal battery further in the winter.